This invention relates to a ventilating apparatus which comprises a fan for ventilating a room, and more particularly to such a ventilating apparatus wherein a human body detector detects the number of persons in the room so that the fan delivers a suitable volume of air in accordance with the result of detection by the human body detector.
It is well known that a ventilating apparatus is provided with one or more detectors for detecting the conditions of a place where the ventilating operation is performed and the operation of a fan of the ventilating apparatus is controlled based on the result of detection by the detectors. Such detectors include a temperature sensor, humidity sensor, air For example, one prior art ventilating apparatus for the ventilation of a living room is provided with a human body detector and an air pollution sensor so that the ventilation is automatically started when one or more persons enter the living room and so that a volume of air delivered by the fan for the ventilation is automatically controlled in accordance with the detected level of air pollution. However, the conventional human body detector can detect the presence or absence of persons but cannot detect the number of persons. Accordingly, it is difficult to control the volume of air suitable for the number of persons in the room.
To solve the above-described problem, the prior art has paid attention to the interrelation between the capacity of a room and the supposed number of persons suitable for the room capacity. When the human body detector detects the presence of one or more persons in the room, the standard volume of air delivered by the fan is controlled so as to be in accordance with the supposed number of persons depending upon the room capacity. When the level of air pollution in the room is raised, the volume of air delivered by the fan is determined by adding the volume of air in accordance with the air pollution level to the standard volume of air.
In accordance with the above-described control method, however, the standard volume of air delivered by the fan is based on the room capacity and not on the actual number of persons in the room. Consequently, the volume of air delivered by the fan becomes too large even when only one person is in a relatively large room, resulting in over driving of the fan.
The air pollution sensor includes a gas sensor for sensing the carbonic acid gas, odor gas and the like. In this respect, the level of room interior air pollution, particularly, the carbonic acid density depends upon the number of persons in the room but the number of persons in the room cannot be exactly detected by the air pollution sensor. The reason for this is that the sensor has only three levels of gas density sensing, that is, the levels of no pollution, low pollution and high pollution and that the air pollution sensor cannot sense the difference in the carbonic gas density in accordance with the number of persons in the room.